Dead coral turning purple?

[Johnny Max]

I set up a small "Opae Ula" brackish water aquarium a little over a month ago.
I put crushed coral and shell substrate in it along with some fossils I have had for years.
But I had a small piece of brain coral. The coral was bleached white.
I have had it since the 80's as part of my tiny shell collection.
I think I bought it from a shell shop on Galveston Beach.
Anyway, It has started to turn purple. It is obvious that is it some form of algae or something.
It has been out of water in a box or on a shelf in our bathroom for over 30 years.
Has anybody experienced anything like this?
What is it?

 

[Tired]

Some sort of algae seems about right. Algae spores are often present in the air, and can be carried in on seaweed and the like. 

 

I have some opae ula, too! Aren't they great? They're so easy to care for. 

[Johnny Max]

1 hour ago, Tired said:

Some sort of algae seems about right. Algae spores are often present in the air, and can be carried in on seaweed and the like. 

I have some opae ula, too! Aren't they great? They're so easy to care for. 

There may have been spores on the coral. I do not think it got in the aquarium from the air because it is only on the coral.

Spores from the air may have gotten on the coral from  when I had it in various places over the years.

[Wingy]

I have that same purple color on some eggshell I tossed in the Opae tank that has black sand.  It seems to be the only thing my Opae don't eat.

[Tired]

It is possible for an algae to grow on one surface, but not others, without having been introduced on that surface. In this case, I would start to wonder if maybe it's something that likes to grow on high-calcium substances. 

[RoyalGramma001]

Maybe red slime algae.

[Leo_ian]

On 12/6/2020 at 1:27 AM, RoyalGramma001 said:

Maybe red slime algae.

cyano bacteria is very different, it looks like a thicker, slimier diatom. And its bright red. i have a small feeling that the algae may be coralline?

[Tired]

Coraline starts in tiny, dense patches, not a thin layer, and is a saltwater algae. I don't think you could get coraline to grow in brackish. If that tank is set up properly for opae ula, it's brackish water.

[Leo_ian]

14 hours ago, Tired said:

Coraline starts in tiny, dense patches, not a thin layer, and is a saltwater algae. I don't think you could get coraline to grow in brackish. If that tank is set up properly for opae ula, it's brackish water.

oh ok, there is a freshwater coralline apparently...

[Tired]

I had to look that up. There is one! Very cool. https://www.nature.com/articles/srep19642#:~:text=Coralline red algae (Corallinophycidae%2C Rhodophyta,important components of marine ecosystems.&text=Although some coralline algae can,or as a living species.

 

There are apparently brackish coralines, too. But they wouldn't be on a saltwater coral skeleton to be introduced as spores, and coraline isn't one of those algaes that just shows up in any available water. It has to be brought in on something. 

 

Regardless, new coraline starts as tiny spots, and expands outward from there. It doesn't start as a really thin layer like in that picture. 

 

OP, has the algae done anything new? 

[farkwar]

Did not know that either

 

Cool